Laparoscopic surgery is a type of minimally invasive surgery in which instruments access internal structures of a patient's body through one or more access devices or trocars. In some laparoscopic procedures, a body cavity is inflated or insufflated with an insufflation gas, for example, carbon dioxide, which provides additional room for manipulating the instruments in the body cavity, thereby facilitating the surgical procedure. The term “pneumoperitoneum” refers to an abdominal cavity in an insufflated state. To maintain pneumoperitoneum, trocars are equipped with one or more seals that prevent insufflation gas from escaping as instruments are inserted, withdrawn, and/or manipulated during an operation. These seals typically comprise elastomeric materials and seal circumferentially against an inserted instrument. Usually, a zero seal and an instrument seal are employed within the trocar.
Numerous technical challenges confront those designing and manufacturing seals for trocars. For example, as an instrument is moved with respect to a seal, the seal will rub against the instrument and create friction. Stiction and hysteresis will also arise. Stiction is the static friction of a stationary instrument in contact with a stationary seal that needs to be overcome to enable their relative motion. Elastomeric seal materials elongate when instruments are inserted, thereby increasing drag force. Oil canning, or the inversion or folding over, of typical seals can also result in loss of precise instrument control and movement because the surgeon experiences a different feedback between large and small changes in the position of the instrument. These aspects, including friction, stiction, hysteresis and oil canning, must be minimized if a seal is to be used in very delicate and precise procedures wherein an instrument must be maneuvered accurately without restriction. Examples of seal technology which overcome these problems include U.S. Pat. Nos. 8,684,975, 8,613,727, 8,562,569, 5,385,553 issued to Applied Medical Resources Corporation and incorporated by reference in their entirety herein. These patents provide floating and pendant seals that are configured to follow the motion of an inserted instrument and allow a minimum sealing pressure upon the shaft of an instrument. The present invention provides a new and improved trocar having a seal with significantly reduced friction, stiction, hysteresis and oil canning properties.